Hopping methods for the detection of QRS onset and offset

Abstract

Disclosed are systems and methods for detecting the QRS portion of an electrocardiogram and also for detect QRS onset / offset points. QRS complexes are identified by testing selected waveform samples to determine if they are in a high curvature region. If a region passes the high curvature test, a verification test is applied to adjacent samples to confirm that the region is within a QRS complex. The search for a QRS onset point begins at an adaptive distance from this region. The curvature of selected regions ahead in the search direction is examined. The search moves past all such high curvature regions. The onset point is then located by searching for a region that is “flat” in either of two senses. First, a region may be locally flat (i.e. small first derivative) in an absolute sense. Second, a region is flat in a relative that further movement away from the interior of the QRS (e.g. toward “earlier” samples) does not result in a significant change in the value of the first derivative. The search is performed by hopping through the waveform samples. Once an onset point is located, the search for an offset point proceeds in a similar manner from a starting point that is an adaptively determined distance from the onset point.

Description

FIELD OF USE[0001]This invention is in the field of medical device systems that process electrocardiograms.BACKGROUND OF THE INVENTION[0002]Heart disease is the leading cause of death in the United States. A heart attack, also known as an acute myocardial infarction (AMI), typically results from a blood clot or “thrombus” that obstructs blood flow in one or more coronary arteries. AMI is a common and life-threatening complication of coronary artery disease. Coronary ischemia is caused by an insufficiency of oxygen to the heart muscle. Ischemia is typically provoked by physical activity or other causes of increased heart rate when one or more of the coronary arteries is narrowed by atherosclerosis. AMI, which is typically the result of a completely blocked coronary artery, is the most extreme form of ischemia. Patients will often (but not always) become aware of chest discomfort, known as “angina”, when the heart muscle is experiencing ischemia. Those with coronary atherosclerosis ar...

AI Technical Summary

Benefits of technology

[0016]An embodiment of the present invention comprises a lead and a processor that computes waveforms from electrocardiograms sensed by the lead. A waveform is scaled so that its overall amplitude (maximum-minimum voltage) is set to a known value. QRS complexes are identifi

Problems solved by technology

AMI is a common and life-threatening complication of coronary artery disease.

Those with coronary atherosclerosis are at higher risk for AMI if the plaque becomes further obstructed by thrombus.

Monitors that include wearable sensors (e.g. a medical-vest with electrodes) may be somewhat inconvenient for patients.

Measuring the ST segment in this fashion may not be optimal in cases where the QRS complex shape changes due to many factors (e.g. axis) shifts.

ST segment changes due to increased heart rate (and other factors) could thus cause somewhat undesired fluctuations if the ST segment is measured at a certain offset from the R wave.

The isoelectric point 1 value is then averaged over 2 samples (16 ms).” This type of searching may be relatively computationally expensive and may also prove problematic with certain types of PQ wave shapes.

Taken together, all of the above mentioned steps are somewhat expensive from the computation and memory standpoints.

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